Organic light emitting diode display device and method for manufacturing the same

ABSTRACT

An OLED display device which prevents a color change according to a viewing angle. The OLED display device may include a substrate defined by a first pixel, a second pixel, a third pixel and a fourth pixel; an anode electrode on the substrate; a first organic light-emitting layer for emitting a first color light; a second organic light-emitting layer for emitting a second color light; a cathode electrode formed of a semi-transparent metal material on the first or second organic light-emitting layer, wherein the first organic light-emitting layer is formed in the first pixel and the second pixel; the second organic light-emitting layer is formed in the second pixel, the third pixel and the fourth pixel; and the second pixel emits mixed light of the first color light and the second color light.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Korean PatentApplication No. 10-2012-0158493 filed on Dec. 31, 2012, which is herebyincorporated by reference as if fully set forth herein.

BACKGROUND

1. Field of the Disclosure

Embodiments of the present invention relate to an organic light emittingdiode display device and a method for manufacturing the same, and moreparticularly, to an active type organic light emitting diode displaydevice and a method for manufacturing the same.

2. Discussion of the Related Art

With the advancement of an information-oriented society, there is anincreasing demand for display devices which display information.Especially, a cathode ray tube (CRT) having a simple driving method anda reasonable price was widely used in an early stage of the displaydevice, thereby enabling popularization of the display device.Thereafter, a liquid crystal display (LCD) device capable of realizingfull colors and wide viewing angle was used as a substitute for CRT.Recently, an organic light emitting diode (OLED) display device has beenattracted as a next-generation flat panel display.

Owing to various advantages such as high resolution, thin profile andlow power consumption, there is an active study for the OLED displaydevice regarded as the next-generation flat panel display, and moreparticularly, for the large-sized OLED display device.

FIG. 1 is a cross sectional view illustrating some parts of the relatedart OLED display device.

As shown in FIG. 1, the related art OLED display device may include asubstrate 101, an anode electrode 110, an organic light-emitting layer120, a cathode electrode 130, a sealing layer 140, and a color refiner150.

First, the anode electrode 110, the organic light-emitting layer 120 andthe cathode electrode 130 are sequentially formed on the substrate 101.The anode electrode 110 supplies a hole to the organic light-emittinglayer 120, and the cathode electrode 130 supplies an electron to theorganic light-emitting layer 120. Thus, when exciton, which is generatedby the supplied hole and electron, falls to a ground state from anexcited state, light is emitted so that the emitted light is supplied todisplay an image on a screen of the OLED display device.

FIG. 1 shows the OLED display device of WRGB method with the colorrefiner 150 for converting a color of white color light into red, greenand blue colors corresponding to the three primary colors. The colorrefiner 150 is formed on the sealing layer 140 above the cathodeelectrode 130, and the color refiner 150 may not be formed in the pixelfor emitting the white color light.

Especially, the organic light-emitting layer 120 may include one or morelight-emitting layers, and the organic light-emitting layer 120 may emitthe white color light obtained by mixture of red, green and blue colors.

Meanwhile, the OLED display device is configured to have a multi-layeredthin film structure, whereby a large amount of light loss might occur inthe interface between each layer. In order to overcome this problem andto improve light extraction efficiency, a microcavity structure may beapplied to the OLED display device. The microcavity structure indicatesa reflection structure which satisfies an optical distance correspondingto an integer multiple of half-wavelength of the light emitted by eachpixel. In this reflection structure, the light reflection is repeated sothat the light is amplified by constructive interference, whereby theamplified light is emitted to the external, thereby improving lightefficiency as compared to the related art.

However, when the white color light emitted by the organiclight-emitting layer 120 including the plurality of light-emittinglayers is amplified through the microcavity structure, and is thenemitted to the external, the color of light may be changed according toa viewing angle due to a plurality of peak wavelengths.

SUMMARY

An OLED display device that may include a substrate defined by a firstpixel, a second pixel, a third pixel and a fourth pixel; an anodeelectrode formed on the substrate; a first organic light-emitting layerfor emitting a first color light, the first organic light-emitting layerformed on the anode electrode; a second organic light-emitting layer foremitting a second color light, the second organic light-emitting layerformed on the anode electrode; and a cathode electrode formed of asemi-transparent metal material on the first organic light-emittinglayer or second organic light-emitting layer, wherein the first organiclight-emitting layer is formed in the first pixel and the second pixel,the second organic light-emitting layer is formed in the second pixel,the third pixel and the fourth pixel, and the second pixel emits mixedlight of the first color light and the second color light.

In another aspect, a method for manufacturing an OLED display device mayinclude forming a reflection layer on a substrate; forming an anodeelectrode on the reflection layer; forming a first organiclight-emitting layer on the anode electrode; forming a second organiclight-emitting layer on the anode electrode, wherein the second organiclight-emitting layer overlaps with the first organic light-emittinglayer; and forming a cathode electrode on the first organiclight-emitting layer or second organic light-emitting layer.

It is to be understood that both the foregoing general description andthe following detailed description of embodiments of the presentinvention are exemplary and explanatory and are intended to providefurther explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a cross sectional view illustrating a related art OLED displaydevice;

FIG. 2 is a cross sectional view illustrating an OLED display deviceaccording to one embodiment of the present invention;

FIG. 3 is a cross sectional view illustrating an OLED display deviceaccording to another embodiment of the present invention;

FIG. 4 is a plane view illustrating a process for forming an organiclight-emitting layer in a method for manufacturing an OLED displaydevice according to one embodiment of the present invention; and

FIG. 5 is a plane view illustrating a process for forming an organiclight-emitting layer in a method for manufacturing an OLED displaydevice of RGB method.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

FIG. 2 is a cross sectional view illustrating an OLED display deviceaccording to one embodiment of the present invention.

As shown in FIG. 2, the OLED display device according to one embodimentof the present invention may include a substrate 201, a reflection layer202, a light-absorbing layer 203, an anode electrode 210, a firstorganic light-emitting layer 221, a second organic light-emitting layer222, a cathode electrode 230, a protection layer 240, a sealing layer250, and a color refiner 260.

First, the substrate 201 may be defined by a first pixel, a secondpixel, a third pixel, and a fourth pixel. For example, as shown in FIG.2, the first pixel may be defined as a blue pixel with a blue colorrefiner (B), the second pixel may be defined as a white pixel with atransparent color refiner or without a color refiner, the third pixelmay be defined as a green pixel with a green color refiner (G), and thefourth pixel may be defined as a red pixel with a red color refiner (R),but not limited to this structure. The pixels may vary in arrangement.

The substrate 201 may be formed of glass or flexible plastic, forexample, polyimide, polyetherimide (PEI), polyethyeleneterepthalate(PET), and etc.

The reflection layer 202 may be formed on the substrate 201. Thereflection layer 202 corresponds to an area, on which light is emittedin a direction of anode electrode 210, in a microcavity structure, andthe microcavity structure is capable of being applied to most of thepixels. Preferably, the reflection layer 202 may be formed on the entirearea of the substrate 201. The reflection layer 202 may be formedbetween the anode electrode 210 and a thin film transistor (not shown).Also, it is preferable that the reflection layer 202 be formed of metalwith high reflectance and conductivity, for example, argentum (Ag) oraluminum (Al).

When a thickness of the metal such as argentum (Ag) or aluminum (Al) isnot more than several-hundred angstrom (Å), the metal shows thetransflective properties which reflects and simultaneously transmitslight. Thus, in order to reflect most of the light, the reflection layer202 is formed at a thickness capable of removing the transflectiveproperties. Preferably, the thickness of reflection layer 202 may be ina unit of micrometer (μm).

Then, the light-absorbing layer 203 is formed on the reflection layer202. The light-absorbing layer 203 may be formed in the second pixel foremitting white color light to the external. The white color lightincludes wavelength ranges corresponding to all visible rays. Thus, onlythe light, which has a predetermined wavelength corresponding to aninteger multiple of optical distance and half-wavelength of themicrocavity structure, is amplified and then emitted to the external.Accordingly, since the white color light is distorted and then emittedto the external, it is difficult to apply the microcavity structure tothe second pixel for emitting the white color light to the external. Thelight-absorbing layer 203 is formed in the second pixel for emitting thewhite color light to the external, which enables light absorption orlight extinction without reflection of the white color light emitted inthe direction of the anode electrode 210.

In order to prevent the reflection of the white color light, thelight-absorbing layer 203 is formed of a material whose reflectance isless than about 10%, preferably. Also, the light-absorbing layer 203 isformed of a material whose optical density (OD) is not more than 3.5,preferably.

Then, the anode electrode 210 is formed on the entire area of thesubstrate 201 including the reflection layer 202 and the light-absorbinglayer 203. A thickness of the anode electrode 210 may be different foreach pixel. The optical distance of the microcavity structure may varyaccording to the wavelength of the light emitted by each pixel. Theoptical distance may be adjusted by the thickness of the anode electrode210. The microcavity structure is not used in the second pixel foremitting the white color light, whereby the thickness of the anodeelectrode 210 may be appropriately determined regardless of the opticaldistance. In case of the first pixel for emitting the blue color light,the relatively-short optical distance is set because the blue colorlight has the relatively-short wavelength, whereby the thickness of theanode electrode 210 for the first pixel may be relatively short.

Meanwhile, the optical distance may be identically set for each of thethird and fourth pixels. The distance corresponding to the least commonmultiple of the half-wavelength of red color light and thehalf-wavelength of green color light is shorter than the thickness ofpixel region. Thus, the thickness of the anode electrode 210 for thethird pixel may be the same as the thickness of the anode electrode 210for the fourth pixel, and the thickness of the anode electrode 210 foreach of the third and fourth pixels may be larger than the thickness ofthe anode electrode 210 for the first pixel. However, it is not limitedto this structure. That is, the optical distance may vary, and the anodeelectrode 210 may vary in thickness.

The anode electrode 210 is formed of a material whose work function islarge so as to supply a hole. For example, the anode electrode 210 maybe formed of a conductive oxide material whose work function is high,wherein the conductive oxide material may be a transparent material, forexample, Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO) or Indium TinZinc Oxide (ITZO).

A lower surface of the anode electrode 210 is connected with the thinfilm transistor (not shown), and an upper surface of the anode electrode210 is connected with the first organic light-emitting layer 221 and thesecond organic light-emitting layer 222, to thereby provide the holefrom the thin film transistor to the first organic light-emitting layer221 and the second organic light-emitting layer 222. The thin filmtransistor may be a driving thin film transistor.

Then, the first organic light-emitting layer 221 is formed on the anodeelectrode 210. The first organic light-emitting layer 221 may be formedin at least one pixel including the second pixel for emitting the whitecolor light. For example, as shown in FIG. 2, the first organiclight-emitting layer 221 may be formed in the first pixel and the secondpixel. Preferably, the first organic light-emitting layer 221 is formedof a material for emitting a blue color, but not limited to the bluecolor.

At least one function layer (not shown) may be interposed between thefirst organic light-emitting layer 221 and the anode electrode 210. Thefunction layer improves mobility of the hole from the anode electrode210 to the first organic light-emitting layer 221. For example, thefunction layer may be a hole injection layer (not shown) and a holetransport layer (not shown). Preferably, these function layers areformed of the material whose hole mobility is relatively higher.

Then, the second organic light-emitting layer 222 is formed on the anodeelectrode 210. The second organic light-emitting layer 222 may be formedin at least one pixel including the second pixel for emitting the whitecolor light. In the second pixel, the first organic light-emitting layer221 and the second organic light-emitting layer 222 may overlap witheach other. Preferably, the second organic light-emitting layer 222 isformed of the material for emitting yellow color light, wherein theyellow color light enables to emit the white color light when it ismixed with the blue color light. However, the colors of light emittedfrom the first organic light-emitting layer 221 and the second organiclight-emitting layer 222 are not limited to the above-described colors.If the conditions that the white color light is made by mixing the firstcolor light emitted from the first organic light-emitting layer 221 andthe second color light emitted from the second organic light-emittinglayer 222 are satisfied, it is possible to provide any mixture of thecolored lights.

At least one function layer may be further interposed between the firstorganic light-emitting layer 221 and the second organic light-emittinglayer 222. That is, a function layer for improving mobility of hole andelectron or a charge control layer may be interposed so as to transportthe hole, which remains after the emission of the first organiclight-emitting layer 221, to the second organic light-emitting layer222, and also to transport the electron, which remains after theemission of the second organic light-emitting layer 222, to the firstorganic light-emitting layer 221. Preferably, the hole transport layermay be positioned adjacent to or may be brought into contact with thesecond organic light-emitting layer 222 provided adjacent to the cathodeelectrode 230. Meanwhile, the electron transport layer may be positionedadjacent to or may be brought into contact with the first organiclight-emitting layer 221 provided adjacent to the anode electrode 210.

As mentioned above, the first organic light-emitting layer 221 and thesecond organic light-emitting layer 222 are overlapped with each otheronly in the second pixel for emitting the white color light, and thesingle light-emitting layer is positioned in each of the remainingpixels, to thereby preventing a color change according to a viewingangle, and showing microcavity effects.

Then, the cathode electrode 230 is formed on the first organiclight-emitting layer 221 and the second organic light-emitting layer222. For the above-described emission method, the cathode electrode 230is formed of the transparent material so that the light is emitted fromthe first organic light-emitting layer 221 and the second organiclight-emitting layer 222 to the external. The cathode electrode 230applies the same voltage to all the pixels, that is, the cathodeelectrode 230 is referred to as a common electrode. Thus, the cathodeelectrode 230 may be formed as a single layer for covering the entirearea of the substrate without patterning. Also, an auxiliary electrodemay be provided and connected with an upper side or lower side of thecathode electrode 230 so as to prevent driving problems caused by theincrease of resistance, to thereby reduce the resistance.

The cathode electrode 230 may be formed of argentum (Ag), magnesium(Mg), aluminum (Al), copper (Cu), or an alloy including any one of theabove materials. Also, the cathode electrode 230 may be formed of metalmaterials with low work function, or their alloys. In order to emit thelight to the external, the cathode electrode 230 is formed of a thinfilm type, that is, the cathode electrode 230 has a thickness which isnot more than several-hundred angstrom (Å).

The cathode electrode 230 again reflects the light, which is reflectedon the reflection layer 202, toward the anode electrode 210, whereby thereflection of light emitted from the corresponding pixel is repeated sothat the light amplified by the constructive interference is emitted tothe external. Through the above microcavity effects, it is possible toimprove light extraction efficiency.

Next, the protection layer 240 is formed on the cathode electrode 230.The protection layer 240 protects the lower structures, which are formedbefore formation of the sealing layer 250, from the following process,and helps the partial reflection of light emitted from the cathodeelectrode 230. For example, the protection layer 240 may be formed ofsilicon nitride (SiNx) or silicon oxide (SiOx).

Then, the sealing layer 250 is formed on the protection layer 240. Thesealing layer 250 may include at least one inorganic film and at leastone organic film which are alternately deposited, wherein the filmconfronting the protection layer 240 and the film confronting the colorrefiner 260 may be formed of the inorganic films. That is, it ispossible to provide the structure of the inorganic film for covering theorganic film.

Thereafter, the color refiner 260 is formed on the sealing layer 250.According to a manufacturing method of the OLED display device, theadditional protection layer 240 or air gap may be positioned between thecolor refiner 260 and the sealing layer 250.

The color refiner 260 may include the blue color refiner (B) formed inthe first pixel, the green color refiner (G) formed in the third pixel,and the red color refiner (R) formed in the fourth pixel. For example,the blue color light is emitted by the first pixel, wherein the bluecolor refiner (B) is formed to represent the precise color. The secondorganic light-emitting layer 222 positioned in the third pixel and thefourth pixel emits the yellow color light, wherein the yellow colorlight is converted into the red color light through the use of red colorrefiner (R) formed in the third pixel, and the yellow color light isconverted into the green color light through the use of green colorrefiner (G) formed in the fourth pixel.

In case of the second pixel, the white color light, which is obtained bymixing the blue color light and the yellow color light respectivelyemitted from the first organic light-emitting layer 221 and the secondorganic light-emitting layer 222, is emitted, wherein the white colorrefiner (W) is formed of the transparent material, or the color refineris omitted.

FIG. 3 is a cross sectional view illustrating an OLED display deviceaccording to another embodiment of the present invention.

As shown in FIG. 3, the OLED display device according to anotherembodiment of the present invention may further include asemi-transparent layer 204 which is formed in a second pixel between ananode electrode 210 and a light-absorbing layer 203.

The white color light is emitted by the second pixel. As describedabove, the pixel for emitting the white color light cannot use themicrocavity structure due to distortion of the white color light.However, if the semi-transparent layer 204, which is formed of asemi-transparent material capable of partially reflecting light, isadditionally provided or the semi-transparent layer 204, which is formedof a material whose refractive index is relatively higher than that ofthe surroundings, is additionally provided, the white color light isslightly amplified within a range of preventing distortion during aprocess for repeating a reflection of the white color light between acathode electrode 230 and the semi-transparent layer 204, and is thenemitted to the external. Accordingly, the semi-transparent layer 204 isadditionally interposed so that it is possible to improve luminance.

FIG. 4 is a plane view illustrating a shadow mask process during amethod for manufacturing the OLED display device according to oneembodiment of the present invention.

As shown in FIG. 4, after aligning a blue shadow mask (BS) having afirst open area which is relatively larger than an area of the firstorganic light-emitting layer 221, wherein the blue shadow mask (BS) isoverlapped with the first organic light-emitting layer 221 so as to formthe first organic light-emitting layer 221 for emitting the blue colorlight, a material for forming the first organic light-emitting layer 221is deposited on the first open area.

Then, after aligning a yellow shadow mask (YS) having a second open areawhich is relatively larger than an area of the second organiclight-emitting layer 222, wherein the yellow shadow mask (YS) isoverlapped with the second organic light-emitting layer 222 so as toform the second organic light-emitting layer 222 for emitting the yellowcolor light, a material for forming the second organic light-emittinglayer 222 is deposited on the second open area. In the second pixel, thefirst organic light-emitting layer 221 and the second organiclight-emitting layer 222 are overlapped with each other, to thereby emitthe white color light obtained by mixing the above blue and yellowcolors.

The first open area and the second open area of the shadow mask (BS, YS)are larger than those of the related art so that it is possible toreduce a mask-manufacturing cost, and to facilitate a process formanufacturing the mask.

FIG. 5 is a plane view illustrating a process for manufacturing a shadowmask of RGB independent deposition method.

As shown in FIG. 5, in case of the RGB independent deposition method,the red pixel (R) is formed by depositing a material for forming a redorganic light-emitting layer in a red open area of a red shadow mask(RS), the green pixel (G) is formed by depositing a material for forminga green organic light-emitting layer in a green open area of a greenshadow mask (GS), and the blue pixel (B) is formed by depositing amaterial for forming a blue organic light-emitting layer in a blue openarea of a blue shadow mask (BS).

The open area in the shadow mask of RGB independent deposition method ismuch smaller than the open area of the shadow mask proposed in themethod for manufacturing the OLED display device according to oneembodiment of the present invention. Thus, if using the shadow mask ofRGB independent deposition method, the time and cost for manufacturingthe mask is increased, and thus the manufacturing cost is alsoincreased.

However, the shadow mask proposed in the present invention has the openarea corresponding to the two or more pixels, whereby it is possible tofacilitate the process for manufacturing the mask, and thus to reducethe manufacturing cost.

According to the embodiments of the present invention, the plurality oforganic light-emitting layers for emitting the different-color light arepartially overlapped so that it is possible to realize the microcavitywithout the color change according to the viewing angle.

Also, the plurality of organic light-emitting layers for emitting thedifferent-color light are partially overlapped so that the open area ofthe shadow mask is maximized in size, whereby the organic light-emittinglayer of the OLED display device is manufactured with easiness.

Furthermore, as the microcavity with the good viewing angle propertiesis applied to the embodiments of the present invention, it is possibleto realize the improved light efficiency and color properties.

According to the present invention, it is possible to increase thelifespan of the OLED display device by improving the light efficiencyand color properties.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to embodiments of the presentinvention without departing from the spirit or scope of the invention.Thus, it is intended that the present invention covers the modificationsand variations of this invention provided they come within the scope ofthe appended claims and their equivalents.

What is claimed is:
 1. An organic light emitting diode (OLED) displaydevice comprising: a substrate defined by a first pixel, a second pixel,a third pixel and a fourth pixel; an anode electrode on the substrate; afirst organic light-emitting layer that emits a first color light, thefirst organic light-emitting layer formed on the anode electrode; asecond organic light-emitting layer that emits a second color light, thesecond organic light-emitting layer on the anode electrode; and acathode electrode of a semi-transparent metal material on one of thefirst organic light-emitting layer or second organic light-emittinglayer, wherein the first organic light-emitting layer is in the firstpixel and the second pixel; the second organic light-emitting layer isin the second pixel, the third pixel and the fourth pixel; and thesecond pixel emits mixed light of the first color light and the secondcolor light.
 2. The OLED display device of claim 1, wherein the mixedlight of the first color light and the second color light has a whitecolor.
 3. The OLED display device of claim 2, wherein the first organiclight-emitting layer emits a blue color light, the second organiclight-emitting layer emits a yellow color light, and the mixed lightcorresponds to a white color light.
 4. The OLED display device of claim1, further comprising: a reflection layer on the substrate, wherein thereflection layer and the cathode electrode are apart from each other bya distance sufficient for satisfying a microcavity condition.
 5. TheOLED display device of claim 4, further comprising a light-absorbinglayer, on the reflection layer of the second pixel, for absorbing themixed light.
 6. The OLED display device of claim 5, further comprising asemi-transparent layer, on the light-absorbing layer of the secondpixel, for reflecting the mixed light.
 7. A method for manufacturing anOLED display device comprising: forming an anode electrode on asubstrate; forming a first organic light-emitting layer on the anodeelectrode; forming a second organic light-emitting layer on the anodeelectrode, wherein the second organic light-emitting layer overlaps withthe first organic light-emitting layer; and forming a cathode electrodeon the first organic light-emitting layer or second organiclight-emitting layer.
 8. The method of claim 7, wherein the substrate isdefined by a first pixel, a second pixel, a third pixel and a fourthpixel, and the first organic light-emitting layer and the second organiclight-emitting layer overlap with each other in any one of the firstpixel, the second pixel, the third pixel and the fourth pixel.
 9. Themethod of claim 8, wherein the first organic light-emitting layer andthe second organic light-emitting layer are formed by the use of shadowmask.
 10. The method of claim 9, wherein an open area included in theshadow mask is larger than an area of at least two of the first pixel,the second pixel, the third pixel and the fourth pixel.
 11. The methodof claim 7, further comprising forming a reflection layer between thesubstrate and the anode electrode.
 12. The method of claim 11, furthercomprising forming a light-absorbing layer on the reflection layer ofthe pixel in which the first organic light-emitting layer and the secondorganic light-emitting layer overlap with each other.
 13. The method ofclaim 12, further comprising forming a semi-transparent layer on thelight-absorbing layer.